The present invention relates generally to rotating equipment and, particularly, to a pumping system in which a pump impeller is mounted to a rotatable shaft.
Submergible pumps are used in a wide variety of environments. One exemplary environment is a subsurface oil reservoir. A submergible pumping system, having a submergible, centrifugal pump, is inserted into the subsurface oil via a wellbore to permit the pumping of oil to a point at or above the surface. Production fluids enter a wellbore via perforations formed in a well casing adjacent a production formation. Fluids contained in the formation collect in the wellbore and may be raised by the submergible pumping system to a collection point above the earth""s surface.
In an exemplary submergible pumping system, the system includes several components, such as a submergible electric motor that supplies energy to a submergible pump. The system may also include a variety of other components, such as motor protectors, pressure and temperature sensing instruments, gas separators and a variety of other components. A connector is used to connect the submergible pumping system to a deployment system. For example, a submergible pumping system may be deployed by production tubing through which production fluids, such as petroleum, are pumped to the surface of the earth. Other deployment systems include cable and coiled tubing.
Power is supplied to the submergible electric motor via a power cable that runs along the deployment system. For example, the power cable may be banded to the outside of the production tubing and directed to the submerged motor.
A typical submergible pump includes several impellers mounted to a shaft for rotation within an outer housing of the pump. A diffuser cooperates with each impeller to guide the fluid in the direction of flow from one impeller to the next sequential impeller. Unlike the impellers, the diffusers are fixed to the outer housing.
The rotatable components on the shaft, such as the impeller, are aligned to cooperate with the fixed components on the outer housing, such as the diffuser. Typically, the clearances between the rotatable components on the shaft and the fixed components on the outer housing are very small. Equipment damage occurs when the rotatable components mounted to the shaft have axial movement independent of the shaft. This is referred to as xe2x80x9cfalse end play.xe2x80x9d For example, if an impeller has sufficient axial movement on the shaft, the impeller may come into contact with a diffuser.
Prior methods of preventing xe2x80x9cfalse end playxe2x80x9d have utilized large and heavy devices with which to lock the parts to the shaft. The masses of these devices and the speeds involved have contributed to accelerated radial wear, leading to premature equipment failure.
It would be advantageous to have a system whereby rotating components could be secured to a rotatable shaft so as to prevent axial movement of the rotating components relative to the shaft and without the problems associated with large, heavy locking devices.
The present invention features a system for securing rotatable components to a rotatable shaft. The system includes a rotatable shaft and first and second stops. The stops form a barrier to axial motion along the rotatable shaft. The system further includes a rotatable component that can be placed on the rotatable shaft between the two stop rings and an expansion assembly. The expansion assembly has an adjustable axial length and is disposed between the second stop and the rotatable component. When the expansion assembly is expanded, it forces the rotatable component against the first stop.
According to another aspect of the invention, a pump is featured that includes a shaft, a plurality of stops, a pump impeller disposed on the shaft between two of the plurality of stops, and an expansion assembly. The stops act as barriers to axial movement of one or more components, e.g., pump impeller, along the shaft. The expansion assembly is disposed along the shaft between the pump impeller and a first stop. The expansion assembly is expandable to force the pump impeller against a second stop.
According to another aspect of the invention, a submergible pumping system is featured that includes a source of rotational motive power and a submergible pump. The submergible pump includes a shaft that is drivingly coupled to the source of rotational motive power. The submergible pump also includes a plurality of stop rings, securable to the rotatable shaft, a rotatable component, and an expansion assembly. The expansion assembly is expandable to hold the rotatable component in place axially on the shaft between two of the plurality of stop rings.
According to another aspect of the invention, a method is provided for securing components to a rotatable shaft. The method includes placing a rotatable component at a desired location on a rotatable shaft. The method also includes securing a first stop to the rotatable shaft adjacent to the rotatable component. The method further includes placing an expansion assembly on the rotatable shaft adjacent to the other end of the rotatable component and securing a second stop to the rotatable shaft adjacent to the expansion assembly. Finally, the method includes expanding the expansion assembly to force the rotatable component against the first stop ring.